Some sources claim 16 hp from factory stamped rockers to 1.6 RR on undercammed underheaded mild 350 engines...
But I think is a bit high too
On a well developed cam/head/exaust engine increased lift and valve acceleration from bigger ratio rocker can offset any possible gain, mainly on exaust due to increased valvetrain instability and too much overlap area to the engine.
Just my $.02
'71 Z28 Pro Street Camaro Pump gas -T-ram - All motor SBC 427" 3308 lbs-leaf spring car-28x10 hoosiers firstname.lastname@example.org - 1/8 mile